Let me get this out of the way. If you like gore please see (possibly buy) this movie. This movie has some of the best (practical?, if it was all CGI I couldn't tell except for a few scenes) gore effects in recent years. A kill in this movie is easily a front runner for kill of the year. The acting was okay, and fans of people under the stairs will be happy to see Roach getting some work in a horror flick. I think its pretty well shot. This leads me to the plot............oh the horror.
The writing in this movie is possibly the dumbest I have ever seen in my 15+ years of watching horror movies. The characters do so many stupid things that it actually hurts the movie...........I can't believe I am saying this. I can usually appreciate horror movies just for the gore but this plot was just too much. Stupid decisions topped by even more stupid decisions. There is a plot twist in the movie that is less of a twist than it is a fun fact. This was just awful, it was like one of those internet stories where dozens of users write it one individual page/paragraph at a time.
So in short, great gore, worst story ever. Myself and my buddies have watched the gore parts on this movie several times, but none of us can stomach the real horror, the plot.